Advanced Nano-based Manipulations of Molasses
in the Cellulose and Paper Discipline:
Introducing A Master Cheap Environmentally Safe
Retention Aid & Strength Promoter in Papermaking
By
*
Tamer Y. A. Fahmy and Fardous Mobarak
Cellulose and Paper Department, National Research Center, Sh. El-Tahrir, Dokki,
Cairo, Egypt.
*
Correspondence to: Dr. Tamer Y. A. Fahmy , Cellulose and Paper
Department, National Research Center, Sh. El-Tahrir, Dokki,
Cairo, Egypt.
E-mail: [email protected]
The original article is available at Carbohydrate Polymers website
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ABSTRACT
This work introduces, for the first time worldwide, molasses -a byproduct
of the sugar industry- as a master retention aid and strength promoter in
papermaking. The paper nanocomposites produced in the present work
-involving molasses, natural cellulose fibers, and kaolin- retained larger
amounts of kaolin while exhibiting greater strength, as compared to their
molasses-free counterparts. Recently, the authors have shown, for the first
time, that the nanoadditive sucrose can overcome the ultimate fate of
deterioration in strength of paper, due to addition of inorganic fillers such
as kaolin. This deterioration was counteracted by incorporating the
nanoporous structure of cellulose fibers with sucrose, which leads to
incorporation beating of the fibers, and thus increases the strength of the
produced paper nanocomposites. In addition, the nanoadditive sucrose
was proven -for the first time- to act as retention aid for inorganic fillers
such as kaolin. We called this phenomenon incorporation retention to
differentiate it from the conventional types of retention of inorganic
fillers. On the other hand, it is well established in the literature that using
gums (including starch) as additives in papermaking enhances the
strength of paper. Molasses contains both the nanoadditive (sucrose), and
gums (including starch). Molasses is a byproduct of sugar industry, which
is cheaper than sucrose; and a major part of sucrose lost in sugar industry
resides in molasses. Moreover, molasses is an environmentally safe
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additive. Therefore, the nanoadditive (molasses) was chosen, in the
present work, to be manipulated as a master strength promoting retention
aid for inorganic fillers used in papermaking, such as kaolin.
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Introduction and Object :The authors and others, in recent work, successfully manipulated
the natural nanoporous structure of cellulose fibers to increase the water
absorption and reactivity of cellulose fibers, to produce water absorbent
paper nanocomposites, or to greatly increase the strength of paper made
from cellulose fibers. This was achieved by incorporating the nanoporous
structure, of water swollen cellulose fibers, by the nanoadditives sucrose
and glucose [1, 2].
It was shown that sucrose and glucose molecules are entrapped in
the cell wall nanopores of cellulose fibers, during the collapse of these
pores, as the fibers are dried. The sucrose and glucose molecules act as
spacers, and prevent the irreversible collapse of the natural nanoporous
structure of cellulose fibers, which -normally- occurs during drying. Thus
the incorporation of sucrose or glucose into cellulose fibers leads to
nanocomposites of increased water uptake (water retention value), and
increased reactivity (i.e. increased accessibility to reagents) [1, 2].
It was, also, shown that incorporating the nanoporous structure of
cellulose fibers, with sucrose, leads to paper nanocomposites of enhanced
strength (breaking length). The cell walls, on both sides of the
incorporated sucrose spacers, are stressed during drying because sucrose
spacers hinder them to relax. This leads to a strain, which makes some
microfibrils partially released and protrude out of the fibers. This in turn
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leads to more efficient entanglement of the fibers, and hence increases the
strength of the prepared paper nanocomposites. In other words, a sort of
fibers beating takes place. The authors and others called this phenomenon
incorporation beating to differentiate it from chemical and mechanical
beatings, conventionally applied to increase the strength of paper [1].
These successful results encouraged the authors to expand the
studies -for the first time- to a sugar industry byproduct rich in sucrose,
which is molasses. Using this byproduct, as an additive for cellulose
fibers, succeeded in producing paper nanocomposites of enhanced dry
and wet strength and improved water absorbance [3, 4].
It is worth mentioning that when aqueous solutions of sucrose are
equilibrated with the water-swollen pulp (cellulose fibers), sucrose should
be able to penetrate into every micropore or nanopore larger than 8 Å
(0.8 nanometer). The volume of these sucrose-accessible pores amounts
to 86.5% of the total pore volume of the micropores. Thus, the dissolved
sucrose molecules should be distributed rather uniformly throughout the
fiber cell wall, except for pores less than 8 Å in size. These calculations
are based on the solute exclusion data of Stone and Scallan and the size of
the sucrose molecules derived from them [5].
Recently [6], the authors succeeded -for the first time- to
manipulate the strength promoting effect of sucrose as a means to
counteract the ultimate fate of deterioration in strength of paper, due to
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addition of inorganic fillers such as kaolin. In addition, sucrose was
proven -for the first time- to act as retention aid for inorganic fillers such
as kaolin. The authors called this phenomenon incorporation retention to
differentiate it from the conventional types of retention of inorganic
fillers [6].
To achieve these aims, the authors prepared an advanced paper
nanocomposite
involving
two
additives
-a
nanoadditive
and
a
conventional additive- within a matrix of natural cellulose fibers. The
first additive (the nanoadditive) is sucrose, which incorporates the
nanoporous structure of the cell walls of cellulose fibers. The second
additive (the conventional additive) is kaolin, the famous paper filler.
Kaolin is enmeshed between the adjacent cellulose fibers. This advanced
paper nanocomposite was prepared by simple techniques [6].
On the other hand, it is well established in the literature that using gums
(including starch) as additives in papermaking enhances the strength of
paper [7].
Molasses contains both the nanoadditive (sucrose), and gums
(including starch). Molasses is a byproduct of sugar industry, which is
cheaper than sucrose; and a major part of sucrose lost in sugar industry
resides in molasses. Therefore, molasses was chosen, in the present work,
to be manipulated as a cheap master retention aid and strength promoter
in papermaking.
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Molasses is an important byproduct of the sugar-extraction process.
The liquid discharged by the centrifugals in the last stage of sugarcane
juice processing, after no more sugar can be separated from the sugarcane
juice by usual factory methods, is called final molasses. Molasses
contains sucrose, which cannot be recovered by economic methods.
Sucrose (lost in molasses) represents the highest proportion of the losses
incurred in the processing of sugarcane. This loss may reach about 9% of
the total sucrose. Thus sucrose lost in molasses is a major consideration,
and is the principal reason for the varied and extensive inquiries which
have been conducted on the profitable utilization of this valuable
byproduct. The sucrose content in molasses may range from about 32% 44%. In addition to sucrose, reducing sugars are present in molasses,
namely glucose and fructose. The content of reducing sugars ranges from
about 10 to 15 percent. Thus the principal value of molasses as an
industrial raw material lies in its content of fermentable sugars, which
amounts to about 50% by weight. Gums (including starch) are also
present in molasses. The content of gums (including starch) ranges from
about 3 to 5 percent by weight [8].
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Materials and Methods: - The cellulose fibers (pulp fibers) used in this work were high alpha
cellulose wood pulp fibers. We have carried out chemical and physical
analyses for this pulp. The results of the analyses and physical properties
are reported in Table 1.
- The conventional additive (inorganic filler kaolin) used in this work was
Egyptian upgraded kaolin prepared on pilot scale, kindly provided by
Metallurgical Research and Development Institute, El-Tebeen, Egypt. Its
specifications and analyses are: Kaolinite 92.43, Al2O3 35.21%, total SiO2
44.43%, Fe2O3 0.92%, TiO2 1.38%, moisture content 0.73%, ash content
87.99%, and brightness 73.90%. The bulk density of this kaolin was
0.846 before grinding and 1.1813 after grinding.
- Filling the cellulose fibers (pulp fibers) with the conventional additive
(inorganic filler kaolin): In all experiments, the cellulosic fibers were mixed with kaolin and
beaten for 15 minutes. The consistency was adjusted to 6%. The fibers
were filled with increasing kaolin quantities (5, 10, 15 and 20g of kaolin
per 100g of pulp fibers).
- Incorporating the nanoadditive (molasses) into the nanoporous structure
of cell walls of kaolin-filled cellulose fibers (pulp fibers): The incorporation methods used in the present work were recently
established by the authors and others [1-4, 6]. After several preliminary
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experiments, we fixed the optimum conditions for manipulating the
nanoadditive (molasses) as a retention aid and strength promoter. The
beaten nondried kaolin-filled fibers were incorporated with molasses
solution of the concentration 10 % w/w, and stirred in the mixer for 15
minutes.
- Paper Sheet Making: Paper sheet composites were made from fibers filled with kaolin only,
and paper sheet nanocomposites were made from molasses-incorporated
kaolin-filled fibers. The paper sheets were prepared according to the SCA
standard, using the SCA - model sheet former (AB Lorenzen and Wetter).
- Determination of the retention value of the inorganic filler kaolin: The amounts of the inorganic filler kaolin, retained in the kaolin-filled
paper sheet composites and in the molasses-incorporated kaolin-filled
paper sheet nanocomposites, were determined by ignition of accurately
weighed paper sheets. The retention value was calculated as the ratio of
the amount of filler retained in the paper sheet to that originally added.
The loss resulting from filler dehydration due to ignition was taken into
consideration [9-11]. The retention value was calculated by the formula:
Retention Value % = (wt of retained kaolin/wt of added amount of kaolin) X 100
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Results and Discussion: 1. Effect of Filling Cellulose Fibers (Pulp Fibers) with the
Conventional Additive (Inorganic Filler Kaolin), in Absence
of Molasses: Table 2 shows the properties of paper composites made from
cellulose fibers, filled with increasing amounts of kaolin (5, 10, 15 and
20g of kaolin per 100g of fibers).
It is evident from Table 2 that the strength (breaking length) of the
paper composites decreased with increasing the amount of added kaolin.
The breaking length of the blank (kaolin-free paper) was 2100 m, while
that of the kaolin-filled paper composites decreased to 1612 m, due to
addition of 20g of kaolin per 100g of fibers. Thus the percentage decrease
in breaking length, due to addition of kaolin, reached 23.24 %.
Also, the wet breaking length of paper composites decreased due to
addition of kaolin. The wet breaking length of the blank (kaolin-free
paper) was 410 m, while that of the kaolin-filled paper composites
decreased to 293 m, due to addition of 20g of kaolin per 100g of fibers.
Thus the percentage decrease in wet breaking length, due to addition of
kaolin, reached about 28.54 %.
This decrease in strength (breaking length) of the paper composites
is a normal phenomenon, observed due to addition of inorganic fillers
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such as kaolin. These fillers are enmeshed between the adjacent cellulose
fibers, and hence interrupt the inter-fiber bonding between adjacent fibers
[7, 9-12].
2. Effect of Incorporating the Kaolin-Filled Cellulose Fibers
with the Nanoadditive (Molasses) on the Properties of the
Produced Advanced Paper Nanocomposites : In these experiments, the beaten nondried kaolin-filled cellulose
fibers (pulp fibers) were incorporated with molasses solution of the
concentration 10 %w/w. Paper sheet nanocomposites were prepared from
these beaten nondried kaolin-filled molasses-incorporated fibers, as
mentioned in the experimental part.
Table 3 shows the properties of paper nanocomposites made from
the molasses incorporated kaolin-filled cellulose fibers, at increasing
amounts of kaolin, of 5, 10, 15 and 20g per 100g of fibers.
It is evident by comparing Table 3 and Table 2 that the breaking
length of paper nanocomposites, produced from molasses-incorporated
kaolin-filled fibers, is greater than that of paper composites produced
from the kaolin-filled molasses-free fibers. This is true for all the added
amounts of kaolin. At addition of 20g of kaolin per 100g of fibers, the
breaking length of the kaolin-filled molasses-free paper composites was
1612
m,
while
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that
of
the
molasses-incorporated
kaolin-filled
paper nanocomposites was 2509 m. Thus, there is a percentage increase
of 55.64 % in the breaking length, due to incorporation of the cellulose
fibers by molasses.
It is evident from Table 3 that the breaking length of the molassesincorporated kaolin-filled paper nanocomposites, even, surpassed the
breaking length of the blank (kaolin-free paper). This was true for all the
added amounts of kaolin. Even at the highest amount of added kaolin
(20g per 100g of fibers), the breaking length of the molasses-incorporated
kaolin-filled paper nanocomposites was greater, by about 19.48%, than
that of the blank kaolin-free paper.
The wet breaking length of paper nanocomposites, produced from
molasses incorporated kaolin-filled fibers, was greater than that of paper
composites
produced
from the
kaolin-filled
molasses-free
fibers
(compare Table 2 and Table 3). This is true for all the added amounts of
kaolin. At addition of 20g of kaolin per 100g of fibers, the wet breaking
length of the kaolin-filled molasses-free paper composites was 293 m,
while
that
of
the
molasses-incorporated
kaolin-filled
paper
nanocomposites was 473 m. Thus, incorporation of the cellulose fibers,
with molasses, led to a percentage increase of 61.43 % in the wet
breaking length.
Table 3 shows that the wet breaking length of the molassesincorporated kaolin-filled paper nanocomposites, even, surpassed the wet
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breaking length of the blank (kaolin-free paper). This was true for all the
added amounts of kaolin. Even at the highest amount of added kaolin
(20g per 100g of fibers), the wet breaking length of the molassesincorporated kaolin-filled paper nanocomposites was greater, by about
15.37 %, than that of the blank kaolin-free paper.
It is clear from these results that incorporating cellulose fibers, with
molasses, succeeded in counteracting the deterioration in strength of
paper, that occurs due to addition of inorganic fillers such as kaolin.
Sucrose -present in molasses- acted as a strength promoter in the paper
nanocomposites, produced from the molasses-incorporated kaolin-filled
fibers. The strength (breaking length) of these paper nanocomposites,
even, surpassed that of the blank (filler-free paper). Incorporating
cellulose fibers, with sucrose, leads to incorporation beating of the fibers,
and thus increases the strength of the produced paper nanocomposites.
Moreover, the gums and starch -present in molasses- exerted an
additional strength promoting effect.
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3. The Role of the Nanoadditive (Molasses) as a
Retention Aid for Inorganic Fillers Such as Kaolin: Table 4 shows the retention value of kaolin for both the kaolin-filled
molasses-free
paper
composites,
and
the
kaolin-filled
molasses
incorporated paper nanocomposites.
It is evident from Table 4 that incorporation of cellulose fibers, by
molasses, resulted in an increase in the amount of kaolin retained in the
produced paper nanocomposites, relative to the case of the molasses-free
kaolin-filled paper composites. This was true for all the added amounts of
kaolin. There was a percentage increase of about 177.54 % in the
retention value of kaolin, due to incorporation of the cellulose fibers by
molasses (at added amount of kaolin of 15 g per 100g of fibers). The
retention value of kaolin in the case of molasses-free kaolin-filled paper
composites was 28.9 %, however, it increased to 80.21 % in the case of
the molasses-incorporated kaolin-filled paper nanocomposites.
These results show clearly that sucrose -present in molasses- acts
as a retention aid for inorganic fillers such as kaolin. It is assumed that,
during paper sheet formation, sucrose decreases the collapse of the
nanoporous structure of the fibers. This collapse -normally- takes place at
paper sheet formation, due to drying of the fibers. Thus, during paper
sheet formation, the sucrose-incorporated fibers are more swollen and
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thicker, relative to the sucrose-free fibers. This fiber swelling decreases
the size of the gaps present between the fibers, during paper sheet
formation. Therefore, lesser amount of inorganic filler can escape through
these narrowed gaps, during the water drainage, which occurs at paper
sheet formation. Eventually, more inorganic filler is enmeshed between
these swollen thickened sucrose-incorporated fibers. We called this type
of retention “incorporation retention” to differentiate it from the
conventional types of retention of inorganic fillers.
Moreover, the gums and starch -present in molasses- exerted an
additional retention aiding effect.
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References
1. Fahmy TYA, Mobarak F, Fahmy Y, Fadl MH, El-Sakhawy M (2006)
Nanocomposites from natural cellulose fibers incorporated with sucrose. Wood Sci.
Technol. 40:77-86
2. Fahmy TYA, Mobarak F (2008) Vaccination of biological cellulose fibers with
glucose: A gateway to novel nanocomposites. International Journal of Biological
Macromolecules 42(1): 52
3. Fahmy TYA (2007) Introducing molasses as a new additive in papermaking. TAPPI
J. 6(8): 23
4. Fahmy TYA (2007) Molasses as a new Additive in papermaking: for high alphacellulose wood pulp. Professional Papermaking 4(1): 42
5. Stone J E, Scallan A M, (1968) Structural model for the cell wall of water-swollen
wood pulp fibers based on their accessibility to macromolecules. Cellulose Chem.
Technol. 2(3):343-58
6. Fahmy TYA, Mobarak F (2008) Nanocomposites From Natural Cellulose Fibers
Filled With Kaolin In Presence Of Sucrose. Carbohydrate Polymers 72(4): 751
7. Casey JP (1962) “Pulp and Paper”, Interscience Publishers Inc., New York
8. Barnes AC (1974) “The Sugar Cane”, World Crop Series, Leonard Hill Books,
London.
9. Mobarak F, El-Shinnawy NA, Soliman AAA (1998) Effect of some chemical
treatments of upgraded Egyptian Kaolin on its retention by bagasse pulp. Journal of
Scientific & Industrial Research 57 (6): 316-323
10. Mobarak F, Augustin H (1976) Cationic starch in papers with high content of bagasse
pulp.2. Influence on filler retention and properties of writing and printing papers.
Papier 30 (3): 100-102
11. Mobarak F, Fahmy Y, Augustin H, (1976) Cationic starch in papers with high content
of bagasse pulp.1. Influence on strength properties of kraft papers. Papier 30 (1): 1619
12. Roberts JC (1996) “Paper Chemistry”, an imprint of Chapmann and Hall.
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Table 1
Analysis and physical properties of the wood pulp
Alphacellulose %
95.00
Pentosanes %
4.09
Ash Content %
0.15
Water Retention Value (WRV) A.D. %
88.82
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Table 2
Effect of filling cellulose fibers (pulp fibers) with the conventional
additive (inorganic filler kaolin) -in absence of molasses- on the
properties of the produced paper composites
Amounts of the added kaolin
(in grams per 100 grams of fibers)
Breaking length in meters
zero
5
10
2100
1925
1851
1773
1612
11.85
15.57
23.24
20
% decrease in breaking length
----
Wet breaking length in meters
410
355
325
311
293
% decrease in wet breaking length
----
13.42
20.73
24.15
28.54
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8.33
15
Table 3
Effect of incorporating the kaolin-filled cellulose fibers with nanoadditive
(molasses) on the properties of the produced advanced paper
nanocomposites
Amounts of the added kaolin
zero
5
10
15
20
2100
2563
2550
2531
2509
% increase in breaking length
----
22.05
21.43
20.52
19.48
Wet breaking length in meters
410
482
478
477
473
% increase in wet breaking length
----
17.56
16.59
16.34
15.37
(in grams per 100 grams of fibers)
Breaking length in meters
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Table 4
The Role of the Nanoadditive (Molasses) as a Retention Aid for the
Inorganic Filler Kaolin
Amounts of the added kaolin
(in grams per 100 grams of fibers)
5
10
15
20
28.11
27.66
28.90
29.72
75.93
77.00
80.21
81.47
170.12
178.38
177.54
174.13
Retention value of kaolin in case of paper
composites produced from kaolin-filled
molasses-free fibers %
Retention value of kaolin in case of paper
nanocomposites produced from
molasses-incorporated kaolin-filled fibers
%
Percentage increase in the retention value
of kaolin, due to molasses-incorporation
into the kaolin-filled fibers %
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